// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains internal routines that are called by other files in
// base/process/.

#ifndef BASE_PROCESS_INTERNAL_LINUX_H_
#define BASE_PROCESS_INTERNAL_LINUX_H_

#include <stddef.h>
#include <stdint.h>
#include <unistd.h>

#include "base/files/file_path.h"

namespace base {

class Time;
class TimeDelta;

namespace internal {

    // "/proc"
    extern const char kProcDir[];

    // "stat"
    extern const char kStatFile[];

    // Returns a FilePath to "/proc/pid".
    base::FilePath GetProcPidDir(pid_t pid);

    // Take a /proc directory entry named |d_name|, and if it is the directory for
    // a process, convert it to a pid_t.
    // Returns 0 on failure.
    // e.g. /proc/self/ will return 0, whereas /proc/1234 will return 1234.
    pid_t ProcDirSlotToPid(const char* d_name);

    // Reads /proc/<pid>/stat into |buffer|. Returns true if the file can be read
    // and is non-empty.
    bool ReadProcStats(pid_t pid, std::string* buffer);

    // Takes |stats_data| and populates |proc_stats| with the values split by
    // spaces. Taking into account the 2nd field may, in itself, contain spaces.
    // Returns true if successful.
    bool ParseProcStats(const std::string& stats_data,
        std::vector<std::string>* proc_stats);

    // Fields from /proc/<pid>/stat, 0-based. See man 5 proc.
    // If the ordering ever changes, carefully review functions that use these
    // values.
    enum ProcStatsFields {
        VM_COMM = 1, // Filename of executable, without parentheses.
        VM_STATE = 2, // Letter indicating the state of the process.
        VM_PPID = 3, // PID of the parent.
        VM_PGRP = 4, // Process group id.
        VM_UTIME = 13, // Time scheduled in user mode in clock ticks.
        VM_STIME = 14, // Time scheduled in kernel mode in clock ticks.
        VM_NUMTHREADS = 19, // Number of threads.
        VM_STARTTIME = 21, // The time the process started in clock ticks.
        VM_VSIZE = 22, // Virtual memory size in bytes.
        VM_RSS = 23, // Resident Set Size in pages.
    };

    // Reads the |field_num|th field from |proc_stats|. Returns 0 on failure.
    // This version does not handle the first 3 values, since the first value is
    // simply |pid|, and the next two values are strings.
    int64_t GetProcStatsFieldAsInt64(const std::vector<std::string>& proc_stats,
        ProcStatsFields field_num);

    // Same as GetProcStatsFieldAsInt64(), but for size_t values.
    size_t GetProcStatsFieldAsSizeT(const std::vector<std::string>& proc_stats,
        ProcStatsFields field_num);

    // Convenience wrapper around GetProcStatsFieldAsInt64(), ParseProcStats() and
    // ReadProcStats(). See GetProcStatsFieldAsInt64() for details.
    int64_t ReadProcStatsAndGetFieldAsInt64(pid_t pid, ProcStatsFields field_num);

    // Same as ReadProcStatsAndGetFieldAsInt64() but for size_t values.
    size_t ReadProcStatsAndGetFieldAsSizeT(pid_t pid,
        ProcStatsFields field_num);

    // Returns the time that the OS started. Clock ticks are relative to this.
    Time GetBootTime();

    // Converts Linux clock ticks to a wall time delta.
    TimeDelta ClockTicksToTimeDelta(int clock_ticks);

} // namespace internal
} // namespace base

#endif // BASE_PROCESS_INTERNAL_LINUX_H_
